本实验是关于data 的exp 一个用户scott 下面imp到另外一个用户 中。 ---------在instance = sheng 的导出scott.emp [Oracle@aora
本实验是关于data 的exp 一个用户scott 下面imp到另外一个用户 中。
---------
在instance = sheng 的导出scott.emp
[Oracle@aoracle ~]$ exp scott/oracle tables=emp file='/u01/rman/file01.txt';
Export: Release 10.2.0.1.0 - Production on Fri Dec 16 09:56:22 2011
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
Export done in US7ASCII character set and AL16UTF16 NCHAR character set
server uses ZHS16GBK character set (possible charset conversion)
About to export specified tables via Conventional Path ...
. . exporting table EMP 14 rows exported
EXP-00091: Exporting questionable statistics.
EXP-00091: Exporting questionable statistics.
Export terminated successfully with warnings.
下面imp到另外一个用户的table 中。
下面建立另外一个user:
SQL> select name from v$tablespace;
NAME
------------------------------
SYSTEM
UNDOTBS2
SYSAUX
USERS
TEMP
SQL> create tablespace TB_DBS datafile '/u02/sheng/tbsdbs01.dbf' size 20m;
Tablespace created.
SQL> select name from v$tablespace;
NAME
------------------------------
SYSTEM
UNDOTBS2
SYSAUX
USERS
TEMP
TB_DBS
6 rows selected.
SQL> create user dbs identified by dbs default tablespace tb_dbs;
User created.
SQL> select username,account_status from dba_users where username like 'DBS%';
USERNAME ACCOUNT_STATUS
------------------------------ --------------------------------
DBSNMP OPEN
DBS OPEN
下面连一下:
SQL> CONN DBS/DBS
ERROR:
ORA-01045: user DBS lacks CREATE SESSION privilege; logon denied
Warning: You are no longer connected to ORACLE.
SQL> grant create session ,resource to dbs;
Grant succeeded.
SQL> conn dbs/dbs
Connected.
SQL> select * from tab;
no rows selected
SQL>
好,,下面把scott 用户下的emp table imp 到dbs 用户下:
[oracle@aoracle ~]$ imp system/manager file='/u01/rman/file01.txt' fromuser=scott touser=dbs;
Import: Release 10.2.0.1.0 - Production on Fri Dec 16 10:54:29 2011
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, OLAP and Data Mining options
Export file created by EXPORT:V10.02.01 via conventional path
Warning: the objects were exported by SCOTT, not by you
import done in US7ASCII character set and AL16UTF16 NCHAR character set
import server uses ZHS16GBK character set (possible charset conversion)
. importing SCOTT's objects into DBS
. . importing table "EMP" 14 rows imported
IMP-00017: following statement failed with ORACLE error 942:
"ALTER TABLE "EMP" ADD CONSTRAINT "FK_DEPTNO" FOREIGN KEY ("DEPTNO") REFEREN"
"CES "DEPT" ("DEPTNO") ENABLE NOVALIDATE"
IMP-00003: ORACLE error 942 encountered
ORA-00942: table or view does not exist
About to enable constraints...
IMP-00017: following statement failed with ORACLE error 2430:
"ALTER TABLE "EMP" ENABLE CONSTRAINT "FK_DEPTNO""
Import terminated successfully with warnings.
SQL> select count(*) from emp;
COUNT(*)
----------
14
SQL> show user;
USER is "DBS"
SQL>

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Efficient methods for batch inserting data in MySQL include: 1. Using INSERTINTO...VALUES syntax, 2. Using LOADDATAINFILE command, 3. Using transaction processing, 4. Adjust batch size, 5. Disable indexing, 6. Using INSERTIGNORE or INSERT...ONDUPLICATEKEYUPDATE, these methods can significantly improve database operation efficiency.

In MySQL, add fields using ALTERTABLEtable_nameADDCOLUMNnew_columnVARCHAR(255)AFTERexisting_column, delete fields using ALTERTABLEtable_nameDROPCOLUMNcolumn_to_drop. When adding fields, you need to specify a location to optimize query performance and data structure; before deleting fields, you need to confirm that the operation is irreversible; modifying table structure using online DDL, backup data, test environment, and low-load time periods is performance optimization and best practice.

Use the EXPLAIN command to analyze the execution plan of MySQL queries. 1. The EXPLAIN command displays the execution plan of the query to help find performance bottlenecks. 2. The execution plan includes fields such as id, select_type, table, type, possible_keys, key, key_len, ref, rows and Extra. 3. According to the execution plan, you can optimize queries by adding indexes, avoiding full table scans, optimizing JOIN operations, and using overlay indexes.

Subqueries can improve the efficiency of MySQL query. 1) Subquery simplifies complex query logic, such as filtering data and calculating aggregated values. 2) MySQL optimizer may convert subqueries to JOIN operations to improve performance. 3) Using EXISTS instead of IN can avoid multiple rows returning errors. 4) Optimization strategies include avoiding related subqueries, using EXISTS, index optimization, and avoiding subquery nesting.

Methods for configuring character sets and collations in MySQL include: 1. Setting the character sets and collations at the server level: SETNAMES'utf8'; SETCHARACTERSETutf8; SETCOLLATION_CONNECTION='utf8_general_ci'; 2. Create a database that uses specific character sets and collations: CREATEDATABASEexample_dbCHARACTERSETutf8COLLATEutf8_general_ci; 3. Specify character sets and collations when creating a table: CREATETABLEexample_table(idINT

To safely and thoroughly uninstall MySQL and clean all residual files, follow the following steps: 1. Stop MySQL service; 2. Uninstall MySQL packages; 3. Clean configuration files and data directories; 4. Verify that the uninstallation is thorough.

Renaming a database in MySQL requires indirect methods. The steps are as follows: 1. Create a new database; 2. Use mysqldump to export the old database; 3. Import the data into the new database; 4. Delete the old database.


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